Quiz on capacitors

[poorguy]

exactly, I remember the faded cloth wrapped wiring and yeah some if not all was hard to figure at best. damn sure had my share of seat of the pants tough dogs as we called them, troubleshooting night mares worked on by the half wit that didn't have a clue before we got them. a simpson 260 vom is what I had and was a must have piece of test equipment. somehow I managed to save enough money to buy a small oscilloscope and man that really made a difference. we used to piggy back capacitors if we thought they were bad that would tell us fast if the hum went away. yeah test equipment was costly but it did pay itself off very fast in my case. I would always try and buy a piece as needed as money would allow. yeah the stuff I dreamed of I now see at flea markets and thrift stores for hardly any money so I buy it and if it can be brought back to life then I try to fix it. poorguy

 

[ICIT2LOL]

Hmm poorguy maybe it needs a dedicated thread as I find this stuff really interesting not only from a personal experience viewpoint but also from a historical one.
I might just post a thread in the chill out room just so that anyone who has interested in this subject / area can discuss what we have been doing already.

It certainly would not hurt for some of the software specialist folks to be able to understand some of the hardware and the properties of it because a lot of the old principles ie Ohms law will always pertain to what we are doing with electronics. I guess it is not everyone's cup of tea but certainly I find it interesting as you do and it has been a real treat going over stuff with you and Jeannie

 

[ICIT2LOL]

Oops missed your post and well we did not have any money and what I got I had to save real hard for. For example the analogue meter was just the ducks guts when I eventually got it and the oscilloscope was just a dream.

I actually have a problem at the moment at my place (when I am there and not at my partners LOL!!) as the stereo I have hooked up to the TV and DVD player / recorder emits a loud hum meaning I cannot use anywhere near the volume I would really like.
Have earthed everything left right and centre , made sure there are no earth loops etc etc but no amount of fixing does anything.
Actually I am wondering if it has something to do with the TV and recorder being two pin power plugs and the stereo if I remember right being a three pin power plug. They all plug into the same surge / power board but like I said nothing seems to get rid of this hum. Any ideas mate??

 

[A Guy]

John, does it hum with no sources connected to it at all? A Guy

 

[mjf]

I got 9/10 because one "answer" was incorrect.

"Is a camera's electronic flash powered by a battery or a capacitor?"
A capacitor is certainly charged to a high voltage and discharged but the flash is still powered by a battery. A flash unit with no batteries and just capacitors would be a hot seller.

 

[Lady Fitzgerald]

...Yep Jeannie I wonder why you missed the air caps in the quiz cos that was what you were using .
The tiny ones we called trimmers - I used to be fascinated by how one could "trim" with those things

Variable capacitor - Wikipedia, the free encyclopedia

As I explained earlier (or I think I did), I haven't seen air gap variable caps used in tuned circuits in fifty years and, back then, only the older style, tube powered equipment had them. Even trimmers had solid dielectrics, same as the tuning caps used in smaller radios. TV tuners had fixed tuned circuits that were switched in and out by being rotated on a drum and used solid dielectric trimmers to fine tune them. My old Heathkit didn't even use trimmer caps on the IF and other fixed circuits; you tuned them by screwing a ferrite core in and out of the coil.

During college, I was too busy trying stay afloat in my classes (I have ADHD, which nobody knew anything about back then; ironically I wound up majoring in Psychology) and, after college, I was too busy trying to make a living to be involved with electronics anymore. Being color blind really limited my ability to work in that field. I challenged the Basic Electricity class (took a test instead of actually taking the class: I did the same for Basic Woodworking Hand tools and aced that one), the only electricity class offered at the college I went to (I had planned on transferring after the first two years), and got only a C because I couldn't read the resistor and mica capacitor values because of my color blindness, even though I knew what the color code was. So, the only air gap caps I've seen in use for the last 50 years have been in antenna circuits for car radios and broadcast antennas and the question was asked in the present tense. As I said, the test was poorly laid out. The person who wrote that test would have flunked my college Psychology Tests and Measurements class.

 

[Lady Fitzgerald]

Oops missed your post and well we did not have any money and what I got I had to save real hard for. For example the analogue meter was just the ducks guts when I eventually got it and the oscilloscope was just a dream.

I actually have a problem at the moment at my place (when I am there and not at my partners LOL!!) as the stereo I have hooked up to the TV and DVD player / recorder emits a loud hum meaning I cannot use anywhere near the volume I would really like.
Have earthed everything left right and centre , made sure there are no earth loops etc etc but no amount of fixing does anything.
Actually I am wondering if it has something to do with the TV and recorder being two pin power plugs and the stereo if I remember right being a three pin power plug. They all plug into the same surge / power board but like I said nothing seems to get rid of this hum. Any ideas mate??

I got to "play" with oscilloscopes when I in High School but never got to own one. The most technical test equipment I ever had was a grid dip meter which I also rigged up to use as a variable test oscillator by making coupling coils for the various tuned circuits it used.

re: the hum. Have you tried plugging the two pin plugs into a different outlet? If the equipment have floating grounds or are grounded through the neutral, that could set up a ground loop. One 'trick" I used to use to get rid of hard to get rid of AC hum in speakers was to put in a bridge attenuator between the speakers and the amp (I used homemade ones but it's easier, and maybe cheaper, to just buy one now. That allowed me to run the amp at higher volume to drown out the hum. Sometimes, reducing the volume of the signal feeding the amp would allow one to crank up the volume to drown out hum but that failed more often than worked.

I haven't used discrete audio components in years; I've been using my computers for audio for the past six or seven years and get better quality than I used to get from the expensive stereo equipment and speakers I used to use in a tiny fraction of the space they used to occupy. The only thing I'm lacking is a radio tuner (for now; the TV tuners I'm planning on putting in my computer for recording OTA shows—and maybe satellite in the future—will be able to play and record FM) but there aren't any radio stations around here (or anywhere else, for that matter) I like well enough to want to bother with a separate one.

 

[ICIT2LOL]

John, does it hum with no sources connected to it at all? A Guy

No mate and the hum is volume related - a bit obvious I reckon and it is logarithmic hum as you might understand.
For example at 5% volume it is bearable at 30% volume - drowns the audio out.

 

[ICIT2LOL]

I got 9/10 because one "answer" was incorrect.

"Is a camera's electronic flash powered by a battery or a capacitor?"
A capacitor is certainly charged to a high voltage and discharged but the flash is still powered by a battery. A flash unit with no batteries and just capacitors would be a hot seller.

Yes technically you are right MJ I guess the devil is in the detail but you have to say too that any cap has to have power before it can be discharged.
So if one was to interpret that the cap is powered up by the battery and the flash produced or in other words powered by the discharge.
In reality I suppose both answers are correct.

 

[Lady Fitzgerald]

John, does it hum with no sources connected to it at all? A Guy

No mate and the hum is volume related - a bit obvious I reckon and it is logarithmic hum as you might understand.
For example at 5% volume it is bearable at 30% volume - drowns the audio out.

That's why an attenuator in the speaker line works (most of the time); it allows you to crank up the volume to drown out the hum without blowing out your eardrums and speakers (not to mention ticking off the neighbors). One downside is an attenuator will reduce bass response but that can usually be compensated for with an equalizer. Still, it's better to find the source of the hum and eliminate it there than to try to cover it up.

 

[ICIT2LOL]

Hmm might just try that Jeannie I have quite a few speakers hooked up to that system (some I made up myself) so losing some of the bass would not bother me too much and as I live on five acres on the edge of a small town neighbours are not a problem

But as you say working out where the hum is coming from is probably best found and eradicated.

 

[poorguy]

good morning to all, a lot of post since I have slept.

ICit2lol, I would 1st check my wall electric receptacle for proper grounding and polarity hot to hot and neutral to neutral. then make sure that your 2 wire power cords are polarized properly again hot to hot and neutral to neutral. try connecting without surge protector to eliminate that it is not the problem. from there I would connect each component up by itself to eliminate each component is not at fault. from there I would check all of my audio input and output cables and cable tv coax to eliminate them. I have found that bad cables can cause noise issues. if none of this works then you might have an issue in one of your pieces of audio/video devices. I have also seen cable tv coax create ground loops that can produce hum between audio and video components. depending on how old you components are it is possible to have a leaky electrolytic causing this hum. hard to say without being where you are having this problem. as Lady Fitzgerald said earlier grounds and neutrals are connected together for noise suppression through coupling capacitors and that could also be an issue if the cap went bad not real likely but possible.

will get back with you guys later I am going to the doctor to get some blood taken.
see you guys in a little bit.
damn interesting conversation we have going on here.
if this thread gets moved let me know some how.
poorguy

 

[strollin]

A little story regarding only using 1 hand when working with electricity.

When I was attending electronics school in the army in 1972, we would be asked to "test" each other by going to a rack of comm equipment and "messing it up" then the other guy would need to correct everything and get the comm equipment back on-line. My favorite thing to do was to disconnect the braided grounding straps that connected adjacent racks together to keep their grounds from floating. I would then chuckle when watching my fellow classmates attempt to reconnect the ground strap. They'd grab the strap attached to rack 1 in left hand, then grab the wing nut on rack 2 to connect the strap but immediately jump back complaining of being shocked. I would then grab strap attached to rack 1 in left hand, touch it to the wing nut on rack 2 then use right hand to tighten wing nut. After that I would use right hand to loosen wing nut then left hand to remove strap. My classmate would then repeat the left hand on strap, right hand on wing nut, shock procedure. Some would not ever pick up what I was doing from observing me and I would have to explain it to them, otherwise they would think that I was simply immune to the shock.

 

[ICIT2LOL]

good morning to all, a lot of post since I have slept.

ICit2lol, I would 1st check my wall electric receptacle for proper grounding and polarity hot to hot and neutral to neutral. then make sure that your 2 wire power cords are polarized properly again hot to hot and neutral to neutral. try connecting without surge protector to eliminate that it is not the problem. from there I would connect each component up by itself to eliminate each component is not at fault. from there I would check all of my audio input and output cables and cable tv coax to eliminate them. I have found that bad cables can cause noise issues. if none of this works then you might have an issue in one of your pieces of audio/video devices. I have also seen cable tv coax create ground loops that can produce hum between audio and video components. depending on how old you components are it is possible to have a leaky electrolytic causing this hum. hard to say without being where you are having this problem. as Lady Fitzgerald said earlier grounds and neutrals are connected together for noise suppression through coupling capacitors and that could also be an issue if the cap went bad not real likely but possible.

will get back with you guys later I am going to the doctor to get some blood taken.
see you guys in a little bit.
damn interesting conversation we have going on here.
if this thread gets moved let me know some how.
poorguy

Right had not thought of the TV coax cable mate and I did check out the earthing on the power sockets and even went to the length of shoving a metal rod into the ground outside and passing the wire back inside and hook it in but that did nothing.
I am guessing now it may well be the age of the stereo as it was purchased in1984 although it was costly at the time it could well be gone.

 

[poorguy]

ok I am back from the doctor.

good story strollin also very true grounding is very important on any piece of energized electrical equipment. speak from hard hitting experience.

ICit2lol, the age of your amp could be a factor. I own a lot of old electronic stuff and have had to work on most of it because it is old. hell I have recapped my tube test instruments all of them. they are 20 to 40 years old, parts go bad. instead of using a grounding rod in the earth take the ground to your electric panel grounding bus bar see if that makes any change.

Lady Fitzgerold, playing with oscilloscopes is fun. I own quite a few of them and connect multiple signal generators to and make all kinds of waveshapes. real bummer no one to help out with the color code, you sound as though you know your way around in this field.

have a great day folks, I am going to work now.

poorguy

 

[Indianatone]

I did the same as you guys. Went to the TV shop when I was 13 or 14 and asked them if I could help myself to some of the TV sets they threw away. Used to get some of them going and watch them. At the time (early 70's) colour TV had started in our area from the 1 megawatt Sandy Heath transmitter so everyone was throwing out there old B&W TV's. Learnt all about them from books and fixing them and got a job fixing TV's at a rental TV chain. Refurbishing colour TV's and mono sets both with valves (tubes) and all transistor. Some sets had the first IC's available to TV manufacturers and also mechanical tuners that covered only the UHF band in some budget sets. The better sets had varicap diodes in the tuners. The old 405 VHF system was finally shut down in 85 and no one noticed apart from an old dear in London with a Philips TV that was 40 years old and Philips gave her a new colour TV and placed her set in a museum. Oh the stuff we fixed in those days, the sets would break down 3 or 4 times a year.

Jonz Old Telly Page

Television History - The First 75 Years

Some of you may find these links of interest

 

[Ranger4]

Hmm might just try that Jeannie I have quite a few speakers hooked up to that system (some I made up myself) so losing some of the bass would not bother me too much and as I live on five acres on the edge of a small town neighbours are not a problem

But as you say working out where the hum is coming from is probably best found and eradicated.

Over the years I have spent a lot of time & money on audio equipment & I have found that hum problems are often caused by earth loops between pieces of equipment.
If they are connected by RCA plugs, you can sometimes just ease the plug out so it's still connected on the centre pin but the earth is open, which may be worth trying on each piece of equipment after disconnecting all the other ones. In other words a process of elimination.

 

[A Guy]

I fix TVs every day. We just swap out boards these days. Changing caps in power supplies is the only component level repair we do these days. And those are few and far between. A Guy

 

[poorguy]

hey all, yeah the last tv shop I worked at we could still do component level repair and most of those were cold solder joints on the high voltage transformer or horizontal output transistor. the printed circuit boards were so flimsy and cheaply made that they created their own problems over a short time.

I am pretty fortunate to work part time at a music store that repairs amplifiers tube and transistor. I am 1 of the 2 techs that are there and I only get the tube amp repair because the other tech doesn't know enough about tubes to troubleshoot them. he is however sharp as hell on the new modern amps and such he just never learned anything about tubes. but still there really isn't enough work to keep both of us there 40 hours a week so part time is good. I'm old.

yeah I remember the old tv repair shop days we would get peoples old tv sets and repair them and sell them used on the floor and most of them were better then the newer sets. old electronics was designed to be repaired and it was made to last. that is why I like working on the old farm tube radios and the old table top tube radios.

have a good day.
poorguy

 

[NoN]

Was too early this morning when answered the quizz so got caught by some (radio, farads)...

Meanwhile, last year i bookmarked for my knowledge the Capacitor Lab page which could be always handy when your board ran out of its warranty, since we're almost concerned by electronics devices involving computing hardwares.